The present invention relates to a display device such as a liquid crystal display and an interface circuit for the display device.
FIG. 6 is a diagram showing the structure of a display device such as a liquid crystal display. In FIG. 6, reference numeral 1 denotes a display screen such as a liquid crystal panel, reference numeral 2 denotes a driving circuit 1 such as a scanning line driving circuit, reference numeral 3 denotes a driving circuit 2 such as a signal line driving circuit, reference numeral 4 denotes a control circuit for generating input signals of the scanning line driving circuit 2 and the signal line driving circuit 3, and reference numeral 5 denotes a power source section for generating reference voltages of a circuit system.
In the structure of the electric circuit of the display device, a signal input from the outside (an input signal in the control circuit 4) includes a clock input signal, a video data input signal, a data enable input signal and other input signals for control (a horizontal synchronizing input signal, a vertical synchronizing input signal and the like). The data enable input signal indicates a valid data period in the video data input signal for a time base, and usually represents a voltage level of H for the valid data period and a voltage level of L for a period other than the valid data period.
FIG. 7 is a voltage waveform diagram showing a signal input to the control circuit 4 every horizontal cycle. In FIG. 7, an axis of abscissa denotes an elapsed time, reference numeral 6 denotes a horizontal synchronizing input signal, reference numeral 7 denotes a data enable input signal, reference numeral 8 denotes a clock input signal, reference numeral 9 denotes a video data input signal, reference numeral 10 denotes a valid data period in the video data input signal, 1CLK denotes a cycle of the clock input signal 8, 1H denotes a cycle of the horizontal synchronizing input signal, an arrow of the clock input signal represents an active edge (a falling edge in the drawing) of the clock input signal 8, the blank portion of the video data input signal 9 represents a valid data period, the oblique line portion of the video data input signal represents an invalid data period, and m represents a screen size (resolution) in a horizontal direction. A voltage level of L in the horizontal synchronizing input signal 6 indicates a reset period, that is, a period in which there is no valid data.
FIG. 8 is a voltage waveform diagram showing a signal to be input to the control circuit 4 every vertical cycle. In FIG. 8, an axis of abscissa denotes an elapsed time, the reference numeral 11 denotes a vertical synchronizing input signal, 1H denotes a cycle of a horizontal synchronizing input signal, 1V denotes a cycle of the vertical synchronizing input signal, the blank portion of a video data input signal represents a valid data period, the oblique line portion of the video data input signal represents an invalid data period, and n denotes a screen size (resolution) in a vertical direction. A voltage level of L in the vertical synchronizing input signal 11 indicates a reset period, that is, a period in which there is no valid data.
As the output signal of the control circuit 4, moreover, a clock signal and a data signal other than the clock signal are generated to be used for the input signal of a driver IC and a driving circuit which generates a signal for driving the control circuit 4, that is, the scanning line driving circuit 2 and the signal line driving circuit 3. The clock signal implies a clock signal to be used in the scanning line driving circuit 2 and the signal line driving circuit 3 (a vertical clock output signal in the scanning line driving circuit 2 and a horizontal clock output signal in the signal line driving circuit 3), respectively. The data signal other than the clock signal implies a video data signal (a horizontal video data output signal) and a control signal other than the video data signal (a horizontal start output signal, a vertical start output signal, a horizontal latch output signal, a horizontal driving voltage polarity control output signal and the like).
However, the kind of the display device is increased with the diversification of the screen size and the resolution in the display device. Consequently, a control circuit 4 for generating a signal to be input to the driver IC and the driving circuit which generate a signal for driving a display screen or a part of the control circuit should be separately developed and fabricated to have a circuit for generating a signal having a timing relationship matched to each kind of the display device. For this reason, a period for the development and a cost of the development become important problems.
In other words, a conventional control circuit or a part of the control circuit can be operated with values of m and n which are uniquely determined for each kind of the display device in FIGS. 2 and 3. Therefore, there is a problem in that the control circuit or a part of the control circuit cannot be used when m and n are not equal to set values or are changed during the display operation.
It is an object of the present invention to provide a display device such as a liquid crystal display and an interface circuit for the display device which can solve the above-mentioned problems and implement an interface circuit for a display device capable of optionally changing a display size (resolution) corresponding to a display screen mode, thereby shortening a period for development and reducing a cost of the development.
In case where the function of optionally changing the display size (resolution) in a display screen mode is to be provided in the prior art, software and hardware of a system for generating an input signal in the display device should be developed. Therefore, there is a problem in that the development and fabrication should be separately carried out for each system.
It is another object of the present invention to provide a display device such as a liquid crystal display and an interface circuit for the display device which can solve the above-mentioned problem, can shorten a period for development and reduce a cost of the development and has the function of easily changing an optional display size (resolution) in a display screen mode by adding a simple circuit.
The present invention provides a display device such as a liquid crystal display and an interface circuit for the display device which have the function of counting a valid data period of a data enable input signal every horizontal cycle and every vertical cycle, holding a count value and generating an input signal in a driver IC and a driving circuit corresponding to a resolution of the display device which is obtained at that time by utilizing a count value held last time for a next horizontal cycle or a next vertical cycle so as to be applicable to the driver IC and the driving circuit which can be used for the display unit having various resolutions, thereby solving the above-mentioned problems to shorten a period of development and to reduce a cost of the development.
The present invention provides a display device such as a liquid crystal display and an interface circuit for the display device which have, in the function of selecting a display screen mode for display with an optional display size (resolution), the function of controlling a valid data period of a data enable input signal corresponding to a display screen mode selected at that time, counting the valid data period of the data enable input signal every horizontal cycle and every vertical cycle, holding a count value and generating an input signal in a driver IC and a driving circuit corresponding to a resolution of the display device which is obtained at that time by utilizing a count value held last time for a next horizontal cycle or a next vertical cycle, and the function of easily changing the optional display size (resolution) in a display screen mode so as to solve the above-mentioned problems and to shorten a period of development and reduce a cost of the development.
The present invention provides a display device such as a liquid crystal display and an interface circuit for the display device have, in the function of selecting a display screen mode for display with an optional display size (resolution), the function of controlling a valid data period of a data enable input signal corresponding to a display screen mode selected at that time and simultaneously recognizing a value of the resolution in response to a selecting input signal to generate an input signal in a driver IC and a driving circuit corresponding to a resolution of the display device and the function of easily changing the optional display size (resolution) in a display screen mode so as to solve the above-mentioned problems and to shorten a period of development and reduce a cost of the development.
The present invention provides a display device such as a liquid crystal display and an interface circuit for the display device have, in the function of selecting a display screen mode for display with an optional display size (resolution), the function of controlling a valid data period of a video data input signal corresponding to a display screen mode selected at that time and generating an input signal in a driver IC and a driving circuit corresponding to a resolution of the display device and the function of easily changing the optional display size (resolution) in a display screen mode so as to solve the above-mentioned problems and to shorten a period of development and reduce a cost of the development.
These objects as well as other objects, features and advantages of the invention will become more apparent to those skilled in the art from the following description with reference to the accompanying drawings.